Cardiac recovery

ABSTRACT

The apparatus includes a flow control conduit ( 2 ) connectable with an output portion of the heart, preferably a bypassed portion of the aorta, and includes a means of feeding heart fluid (R/O), for example blood or cardioplegia into the heart. The flow control device ( 1 ) includes in communication a variable resistance pressure control means ( 4 ) which is variably biased to a closed position to maintain on the bypassed heart region a predetermined level of pressure, to facilitate the creation of back pressure during filling of the bypassed heart region or a beat or pumping phase of the heart, and when the heart fluid pressure increases to reach a predetermined threshold, the pressure control means facilitates a release of fluid from the conduit, thus facilitating expulsion of potential emboli from the bypassed heart region, and enabling “cycling” of the heart while in a bypassed condition, prior to the bypassed region being taken off bypass. The invention includes preferred and alternative embodiments of variable resistance pressure control means including a hollow deformable bladder ( 16 ) biased by a compressible control fluid externally of said bladder.

[0001] This invention relates to cardiac surgery and more particularlyto an apparatus and method of use of such apparatus in cardiac bypasssurgery recovery with the aim of minimising dangers of such surgeryparticularly in the recovery phase.

BACKGROUND TO THE INVENTION

[0002] Cardiac surgery, particularly open heart surgery has and remainsto be associated with significant risk to the patient, neverthelessthere is a trend of incremental developments in surgery techniques andapparatus which tends to reduce risks in the operation.

[0003] It has long be recognised, for example by research into theeffects of nitrogen narcosis (the bends), gas embolisms and the likemanifesting in gas bubble entrainment within the body's vascular systemcan have adverse effects, such as subsequently impaired brain functionor neurocognitive deficits.

[0004] It is implicit that in most cases open heart surgery carries withit at least a risk of gas bubble (normally air) and particulate embolientrainment in the vascular system as a result of the interior of theheart, or the blood vessels associated with the heart becomingpunctured, disconnected and open to atmosphere.

[0005] In the past, toward completion of a bypass open heart operation,as the surgical repairs are completed, the operating staff undertakevarious steps in order to “flush” or “bleed” the bypassed region in anendeavour to remove all potential emboli, for example air bubbles,particles and the like from the heart and the associated bypassedvascular system. Such steps have typically included “bleeding” theregion via a puncture in the aorta coupled with careful filling of theheart with cardioplegia or blood, aspirating the heart at variouspositions for example by syringe punctures, coupled with physicalmanipulation of the heart, for example by squeezing, tilting, suctionventing and the like.

[0006] Whilst such steps tend to remove most of entrained emboli fromthe heart and the associated bypassed region, in view of the “cavitied”structure of the heart and associated blood vessels, coupled with thebuoyancy of gas bubbles and their tendency to “adhere” to adjacentsurfaces, it has been found inevitable that gas bubbles remain in thebypassed region. Tests have shown that despite the most diligentattention to emboli removal, these techniques are not completelyeffective; at re-instatement of normal circulation by removal of theaortic clamp, gas bubble numbers in the region of 1000 to 5000 atclosure of the operation are commonly detected being expelled by therecovered heart and its associated blood vessel system. These bubblesare then transported to the body organs.

OBJECTS OF THE INVENTION

[0007] It is an object of this invention to provide an apparatus and/ormethod of use of such apparatus which at least comes some way inaddressing the problems abovenoted, or at least provide the public witha useful choice.

[0008] Other objects of this invention will become apparent from thefollowing description.

BROAD DESCRIPTION OF THE INVENTION

[0009] According to one aspect of this invention there is provided afluid control device adapted for communication with a fluid supply, saidflow control device including a pressure control means adapted tocontrol a fluctuating fluid pressure in said device wherein saidpressure control means is normally biased toward a closed position formaintaining a predetermined level of upstream backpressure, but isopenable under the bias under predetermined additional pressure torelease fluid from said fluid control device, said pressure controlmeans providing a bias which is proportional to an extent of opening ofsaid pressure control device and the predetermined additional pressure.

[0010] According to a further aspect of this invention there is provideda fluid control device adapted for connection in controlledcommunication with a bypassed heart region, and a heart fluid supply forsaid bypassed heart region, said fluid control device including avariable resistance pressure control means adapted to control heartfluid flow from, and/or fluctuating pressure in, said bypassed heartregion, said pressure control means including an opening incommunication with said bypassed heart region normally biased toward aclosed position for maintaining a predetermined level of upstreambackpressure, but variably openable against the bias under predeterminedadditional heart fluid pressure in said bypassed heart region to releasethrough said opening heart fluid from said bypassed region, saidpressure control means providing a bias which is proportional to across-sectional area of the opening in said pressure control means andthe predetermined additional heart fluid pressure in said bypassed heartregion.

[0011] According to a still further aspect of this invention there isprovided a method of improving the removal of potential emboli from abypassed heart region prior to removal of said region from bypassincluding the steps of connecting a fluid control device incommunication with an output portion of said bypassed heart region, saidfluid control device having a variable resistance pressure controldevice in communication with said bypassed heart region capable ofreleasing heart fluid from said fluid control device over apredetermined pressure, filling said bypassed heart region with heartfluid and allowing said heart to pump said heart fluid whilst in abypassed condition, and whilst maintaining an inflow of heart fluid tosaid bypassed heart region.

[0012] According to a still further aspect of this invention there isprovided a system for reducing potential emboli from a bypassed heartregion prior to removal of said region from bypass, a fluid controldevice adapted for connection in controlled communication with abypassed heart region and a heart fluid supply for said bypassed heartregion, said fluid control device including a variable resistancepressure control means adapted to control a heart fluid flow from and/orpressure in said bypassed heart region, said pressure control meansnormally biased towards a closed position, but openable against the biasunder predetermined heart fluid pressure in said bypassed heart regionto release heart fluid from said bypassed heart region, said pressurecontrol means providing a bias which is proportional to cross-sectionalarea of an opening in said pressure control means and heart fluidpressure in said bypassed heart region.

[0013] According to a still further aspect of this invention there isprovided a fluid control device including a conduit assembly connectablefor controlled communication with a bypassed heart region and a venousline of a body vascular system including a variable resistance pressurecontrol means variably biased to a normally closed position formaintaining a predetermined level of upstream backpressure and openableunder additional predetermined aortic heart fluid pressure to at leastpartially control fluctuating heart fluid pressure in the bypassed heartregion, said fluid control device connectable with a fluid reservoirand/or oxygenation device for circulation of heart fluid between saidbypassed heart region and said fluid reservoir and/or oxygenation devicewhilst said bypassed heart region is at least partially bypassed, saidpressure control means adapted to control the fluctuating heart fluidpressure in said at least partially bypassed heart region during heartfilling and subsequent heart pumping; where said heart moves heart fluidin said bypassed portions of said heart during a recovery period, priorto completion of removal of said bypassed heart region from the bypassedcondition.

[0014] Other aspects of this invention which should be considered in allits novel aspects will become apparent from the following description.Modifications are envisaged and may be incorporated without departingfrom the scope or spirit of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015] The preferred form of the invention will now be described withreference to the accompanying drawings in which:

[0016]FIG. 1. is a substantially diagrammatic view of a typicaltraditional bypass circulatory system used when conducting heart bypasssurgery.

[0017]FIG. 2. is a similar view to FIG. 1, however showing the apparatusof this invention and its method of use in bypass heart surgery.

[0018]FIG. 3. is a substantially diagrammatic cross-sectional sideelevation of a preferred pressure control means according to theinvention.

[0019]FIG. 4. is an assembly drawing of a typical fluid control deviceof this invention showing the variable resistance flow control means inpartial cutaway form.

[0020]FIG. 5. is an assembly drawing of a further embodiment of the atypical fluid control device of FIG. 4 of this invention showing thevariable resistance flow control means in partial cutaway form.

[0021]FIG. 6. is a substantially diagrammatic side view of a pressurecontrol means according to an alternative embodiment of the invention.

[0022] The preferred form of the invention is also described withreference to a paper headed “A Novel Dual Vent Left Heart De-AiringTechnique Markedly Reduces Carotid Artery Micoemboli After ValveSurgery” by the inventor F P Milsom FRACS (unpublished).

[0023] Referring generally to the drawings, it will be appreciated thatFIGS. 1 and 2 show substantially diagrammatically in disposition anormal heart bypass assembly configuration, although this configurationcan vary in certain circumstances. It is to be assumed that the heart H,aorta A and vena cavae V are substantially in a disposition of that of apatient undergoing open heart surgery.

[0024] An aortic clamp AC is shown diagrammatically at a portion of theaorta remote from the heart H and is in the substantially traditionalform.

[0025] Venous blood from the body vascular system is drawn off the venacavae VC or alternatively, the right atrium (not shown), via a gravityvenous drain engaged through a predetermined puncture in the vena cavaeVC or right atrium, leading to a reservoir/oxygenation apparatus R/O ofsubstantially known construction. The reservoir/oxygenation apparatusR/O also provides for de-bubbling or de-aeration and reoxygenation ofthe blood prior to it being returned to the body vascular system via apump P1 for example a roller pump and an aortic feed AF line whichterminates in the aorta A downstream of the aortic clamp on a side ofthe aortic clamp AC remote from the heart H.

[0026] In addition to the venous drain VD frequently a further leftventricular drain LV extends from insertion from the heart H leftventricle (not shown), to the inlet side of the reservoir/oxygenatorapparatus R/O preferably via a second pump P2. In this way it will beappreciated that blood flow through the heart H and the associated bloodvessels can be bypassed to enable open heart surgery.

[0027] Referring to FIGS. 2 and 3 in particular, and also FIGS. 4 and 5,it will be appreciated that in FIGS. 1 and 2 the “normal” bypassassemblies are shown in broken lines whereas in FIG. 2, the apparatus ofthis invention is shown in solid lines (with the exception of thediagrammatic representation of the heart H, aorta A and vena cavae VC).

[0028] The apparatus is formed in suitable materials includingappropriately graded plastic materials, metals and the like, althoughthe invention is not limited to such materials and alternative suitablematerials may be provided.

[0029] With reference to FIG. 2, the apparatus as generally indicated byarrow 1 include an arterial line 2 preferably formed in suitableflexible pipework material, which is arranged at an inlet end 3 tocouple, for example by a suitable T or Y connector or the like (notshown), with an outlet portion of the reservoir and oxygenator R/O, suchthat oxygenated blood, or alternatively cardioplegia can be supplied tothe arterial line 2.

[0030] A pump P3 is provided on the arterial line, for example asuitable roller pump or the like, to provide fluid flow through the line2 at a predetermined flow and pressure rate. The arterial line 2terminates in communication with the aorta, preferably via apredetermined puncture through the aortic wall upstream of the aorticclamp AC, such that on operation of the pump P3, blood and/orcardioplegia, can be supplied to the aorta and via the aorta the heartin a controlled manner to allow for use of line 2 throughout procedureand preferably during recovery of the heart H after surgery.

[0031] The arterial supply line 2 is also arranged in communication witha pressure control valve adapted to provide a variable resistance tofluid flow in the arterial supply line 2. The pressure control valve 4as depicted in FIGS. 2 and 3 is a preferred form of such a valve,however, in alternative forms of the invention alternative pressurecontrol valves can be utilised with the apparatus of this invention.

[0032] The pressure control valve 4 in the preferred form of theinvention has an intended high pressure side 5 connected, for example bysuitable fittings, pipework and the like with the arterial supply line2. The pressure control means 4 is preferably variably adjustable in itsresistance and is controllable to provide a closed position, yet is ableto open against a bias on a preferably progressive basis, dependent onthe pressure found in the arterial supply line 2 upstream at the valve,thus the pressure control means 4 provides in effect a variableresistor.

[0033] An intended low pressure side 6 of the pressure control means 4provides a return line 7 preferably in the form of a conduit coupledwith the intended low pressure side 6 of the pressure control means 4and in communication via suitable pipework, for example a T or Yconnector and the like with the venous drain VD.

[0034] The apparatus, preferably but not essentially also includes aleft ventricular drain 8 which is also in communication with theintended low pressure side 6 of the pressure control means 4. In thepreferred form of the invention, preferably in use, the left ventriculardrain LV as shown in FIG. 1 (and also FIG. 2 in varied form) iscontrolled by gate valves generally indicated by arrows GV, for couplingof the left ventricular drain LV to the intended low pressure side 6 and“in circuit” to the reservoir and/or oxygenator device R/O.

[0035] Suitable monitoring apparatus 9 are preferably provided formonitoring pressure within the arterial supply line 2 and on the lowpressure side 6 of the assembly. Preferably such monitoring arrangementsinclude electronic display apparatus and also optionally includeinteractive and response initiating apparatus dependent on predeterminedcriteria, controlled by use of integrated circuits such as comparatorsand the like.

[0036] Referring to FIG. 3 in particular, it will be appreciated that inthe preferred form of the invention, the pressure control means 4 in thepreferred form of the invention is adapted for use in the apparatus andfor coupling with remaining portions of the apparatus in a suitablespigot/socket arrangement, incorporating appropriate clamps and thelike. The pressure control apparatus 4 is provided with a pair of endportions, preferably moulded in suitable plastics materials and the likeincorporating an inlet bore 11 in the case of the intended high pressureof the apparatus and an outlet bore 12 in the case of the intended lowpressure side 6.

[0037] Each of the fittings 10 are provided with an inner-spigot 13 isprovided of a substantially friction tight fit with an open end portion14 of a housing 15. Preferably the housing 15 and associated spigotportions 13 are of substantially round or annular cross-section,although this is in no way essential to the invention and in thepreferred form of the invention, preferably the body portion is formedof a substantially clear plastics material so as to enable visiontherethrough.

[0038] The pressure control means 4 is formed in suitable materials in asubstantially unitary structure, for example incorporating the housing15 and bladder portions conjoined with one another, for example by radiofrequency welding, solvent gluing or bimoulding and the like, such thatthe apparatus is formed in an integral unit, or a substantially integralunit and in a way which is convenient for economic production andconvenient disposability of the unit after use.

[0039] A deformable bladder member 16 is, in the preferred form of theinvention, provided to engage within the housing 15 and between thefittings 10. In the preferred form the bladder member 16 is formed ofrelatively thin and pliable material, for example clinical grade elasticsilicone, PVC, or other flexible or elastomeric materials and in asubstantially tubular configuration of a diameter that, in a relaxedstate, outer surfaces 16 a are able to lie substantially injuxtaposition with interior faces 15 a of the housing 15 and where endportions 17 of the bladder 16 are able to flare outwardly about ends ofthe housing 15, to terminate in portions engaged snugly about exteriorsurfaces of the housing end portions 14.

[0040] It will be appreciated that by frictional engagement of these endfittings 10 spigots 13 in the housing end portions 14, portions of thebladder are sandwiched therebetween, to create a convenient and fluidtight seal and furthermore, to provide a variable conduit through thevalve 4 from the inlet bore 11 to the outlet bore 12 which is readilyable to be assembled in a sterile form yet which is substantiallymechanically robust; while a friction fit is disclosed as a preferredoption, it will be appreciated that the assembly could be subject togluing or welding as an alternative.

[0041] The housing 15 in the preferred form of the inventionincorporates a control assembly as generally indicated by 18 andpreferably includes a spigoted port 19 which passes through the housing15 wall to enable connection of a control conduit 20 therewith. The port19 in some cases can be also provided with a non-return valve (notshown).

[0042] It will appreciated that cross-sectional area of the availablepassageway through the pressure control means 4 can be varied accordingto the extent of control fluid which fills a chamber 21 which can beestablished by control fluid being pumped into the chamber 21 via thecontrol conduit 20.

[0043] Although this is in no way essential to the invention, thecontrol fluid used for the chamber 21 is a compressible gas, however inalternative forms of the invention, other fluids can also be utilised,subject to appropriate pressure control apparatus being provided.

[0044] It is envisaged that in one embodiment there will be aninterconnection between the control fluid volume and/or pressure appliedto the chamber 21 and the detected pressure within one or both of thearterial supply line or parts of the assembly on the low pressure side 6of the pressure control means 4.

[0045] Alternatively, it is envisaged that the pressure/volume ofcontrol fluid for the chamber 21 can be influenced by other pressureand/or flow rates within the apparatus or the heart H, the aorta orelsewhere in the body vascular system.

[0046] It should be understood that in alternative embodiments of theinvention and as shown in FIG. 5 a “smoothing” of flow through thearterial supply line 2 upstream of the pressure control valve 4 can beachieved by mounting a number of pressure control valves 4 incommunication in series with a small reservoir therebetween. In thisway, it will be appreciated that a flow resistance can be reduced over asingle valve assembly 4 as previously described where a pressuregradient between control fluid in the chamber 21 and the passageway oropening through the deformable bladder member 16 is reduced, thusenabling pressure to be maintained on the arterial supply line 2 and thebypassed heart region sufficient to provide perfusion of the tissue inthe bypassed heart region during a rest phase yet maintaining relativelylittle resistance to flow when the passageway through the bladder 16opens under increased heart pumping pressure during a pumping phase.

[0047] In a further alternative embodiment of the invention and as shownin FIG. 6, a further alternative arrangement for “smoothing” of flowthrough the arterial supply line 2 to upstream of the pressure controlvalve can be achieved by providing an alternative assembly of pressurecontrol means as generally indicated by arrow 4 which is preferablyformed as a flexible envelope formed from flexible sheet material todefine a serpentine labyrinth passageway between the intended highpressure side 5 and the intended low pressure side 6.

[0048] A controllable variable clamping means 30 is arranged forclamping across the flexible envelope to provide a variable clampingaction on the envelope, to have the effect of variably restricting thelabyrinth passageway.

[0049] It is intended in this form of the invention that the envelope beprovided, for example in suitable plastics sheet material suitablywelded together, for example by fusion welding and the like to achievethe structure in an economical, sterile manner as appropriate to theconditions of use.

[0050] The abovementioned alternative embodiments of pressure controlarrangements are intended to closely approximate a natural pressure andoperational situation for the heart.

[0051] Use of the apparatus 1 according to the invention is intended asan integrated assembly such as that depicted in FIGS. 4 or 5 connectedinto the bypass equipment as shown diagrammatically in FIG. 2, as theopen heart surgery operation is reaching a conclusion and where theheart H is required to be resuscitated.

[0052] Preferably installation of the apparatus 1 assembly is donepartially, at commencement of the bypass procedure, in conjunction withsuch bypass procedure, or alternatively immediately prior to heartresuscitation at conclusion of the surgical procedures phase. Atsubstantial completion of the surgical procedures on the bypassed regionthe heart H is resuscitated, flushed with cardioplegia and subsequentlyarterial blood simultaneously with continuation of the normal byseparate bypass blood circulation.

[0053] In the preferred operation, suitable valving/pump/supplyconnections (not shown) enabling supply of cardioplegia and blood to thearterial supply line 2 and the pump P3 is operated to infuse the heart Hvia the portion of the aorta A upstream of the aortic clamp AC as shownby broken flow lines in FIG. 2. The effect of filling the heart H inthis way enables the surgeon to manipulate the heart and to removesignificant quantities of mixed fluids, for example gases and particlesand other emboli and begin the heart H resuscitation process.

[0054] It will be appreciated that upon the heart H and associatedbypass vessels filling, such portions will be substantially protectedfrom undue dilation by the pressure control means 4 which, having beenpreviously set to a predetermined and possibly variable pressure remainsclosed, until such time as such predetermined pressure is reached. Thispressure threshold is reached, for example by pump 3 pressure oralternatively, by pressure on the heart H starting to beat, and controlsthe pressure on the heart H and bypassed region through discharge ofsufficient cardioplegia blood from the arterial supply line 2 throughthe pressure control means 4 a pressure in excess of a predeterminedpressure be encountered therein. Blood/cardioplegia flow on heart H beatpumping is shown by solid flow lines of FIG. 2.

[0055] The pressure control means 4 constructed in the arrangementdescribed, by virtue of the bias created on the bladder 16 facilitatesthe creation of “backpressure”, in the apparatus and thus in thebypassed heart region, and during filling of the heart or a beat orpumping phase of the heart, it is only when the heart fluid pressureincreases to reach a predetermined threshold that a flow of heart fluidthrough the pressure control means 4 occurs; the extent or volume ofthat flow being controlled by the variable resistance created by thevalve means in proportion to the additional pressure created. Thecross-sectional area of the opening or passageway through the bladder 16is thus proportional to the additional created pressure over thepredetermined threshold; this environment approximates a naturalsituation for the heart.

[0056] In an alternative arrangement, it is anticipated that thepressure at which the control means 4 releases pressure, can be varied,according to an automatic, such as “feedback control” from pressurewithin the remaining parts of the apparatus 1, or alternatively, by wayof control by sensors placed at strategic and predetermined positions inthe downstream portion of the bypassed region, or the heart H.

[0057] As the heart H commences to beat, it will be appreciated that theheart H can pump through a circuit upstream of the aortic clamp AC andthrough the reservoir/oxygenation apparatus R/O, effectively reversingthe blood flow through the portion of the arterial supply line 2downstream of the pump, but upstream of the pressure control means 4,thus enabling the heart H to pump while the aortic clamp AC is closed,until such time as the surgeon is satisfied that all potential emboli,for example gas bubbles or particles which would otherwise have beenentrained within the heart H and associated bypassed region have beenremoved by the heart H pumping action and furthermore, that in all otheraspects the patient can come “off” bypass.

[0058] Upon the above-mentioned happy situation having been reached, thesurgeon is then able to release the aortic clamp AC to enable naturalaortic blood flow and then attend to removal of the apparatus 1 and thebypass apparatus, prior to completion of other aspects of the operation.

[0059] It will be appreciated that in view of the manner in which thechamber 21 of the pressure control valve 4 is filled in the preferredform of the invention with a compressible gas, a restriction provided bythe pressure control means is variable, proportionately to the pressureon the bladder 16 on the normally high pressure side 5, such that as theheart H begins to resuscitate and subsequently increases in strength andpumping capacity the volumetric capacity of the passageway through thebladder and thus the level of restriction is reduced; enablingcirculation of blood/cardioplegia possibly containing potential emboliand subsequent non-potential emboli containing blood independently ofthe bypassed normal body vascular system.

[0060] It will be appreciated that the pressure control means 4 provideresistance against which the heart can pump, with the flow rate andpressure being proportional. In this way, the bias of the pressurecontrol means 4 can be adjusted to maintain a sufficient predeterminedrest state pressure in the arterial line 2 which facilitates perfusionof the bypassed heart region and which can approximate a normalenvironment against which the heart normally pumps together withrelatively low resistance to flow on the heart beat pumping action ofthe heart.

[0061] Whilst the invention has been described with reference to aparticular type of pressure control means, it is to be understood thatthe invention is not limited to such a pressure control device 4.

[0062] Furthermore, whilst the pressure control device 4 described isshown as a pressure control means and/or restrictor for cardiac recoverymeans, it is envisaged that the valve/ restrictor apparatus may alsohave alternative applications, particularly but not exclusively wherethe construction and arrangement facilitating convenient sterilisationand promotion of sterile conditions is required.

[0063] It will be appreciated that the substantially “automatic”variation of control of blood pressure and flow rate, convenientlyenables de-aeration of the bypassed portions without the need for directattention of the surgeon at a time when it may well be divertedelsewhere, such as ensuring that other operative work is holding up andthat the patient's vital signs are returning.

[0064] It will appreciated that in certain circumstances, the abilityfor the pressure control means to fluctuate the extent of restrictionand thus the flow rate and pressure, actively, in response topredetermined criteria and/or sensors, such as the monitoring apparatus9 described with reference to FIG. 2 further may enable the surgeon'sattention to be safely diverted elsewhere.

[0065] Thus by this invention there is provided an apparatus for cardiacrecovery and/or a method of use of such apparatus which facilitatesimproved patient safety and improved quality of cardiac recovery inbypass surgery.

1. A fluid control device adapted for communication with a fluid supply, said fluid control device including a pressure control means adapted to control a fluctuating fluid pressure in said device wherein said pressure control means is normally biased toward a closed position for maintaining a predetermined level of upstream backpressure, but is openable under the bias under predetermined additional pressure to assist release of fluid from said fluid control device, said pressure control means providing a bias which is proportional to an extent of opening of said pressure control device and the predetermined additional pressure.
 2. A fluid control device adapted for connection in controlled communication with a bypassed heart region, and a heart fluid supply for said bypassed heart region, said fluid control device including a variable resistance pressure control means adapted to control heart fluid flow from, and/or fluctuating pressure in said bypassed heart region, said pressure control means including an opening in communication with said bypassed heart region normally biased toward a closed position for maintaining a predetermined level of upstream backpressure, but variably openable against the bias under predetermined additional heart fluid pressure in said bypassed heart region to release through said opening heart fluid from said bypassed region, said pressure control means providing a bias which is proportional to a cross-sectional area of the opening in said pressure control means and the predetermined additional heart fluid pressure in said bypassed heart region.
 3. A fluid control device as claimed in claim 2 wherein a portion of said fluid control device is arranged to act in use as a conduit for controlled communication between the bypassed heart region and a supply of heart fluid for said heart to facilitate flushing of said bypassed heart region and/or operation of said bypassed heart region while at least partially bypassed, said pressure control means adapted to restrict the heart fluid pressure in said at least partially bypassed heart region and said device to a predetermined level.
 4. A fluid control device as claimed in claim 2 connectable in controlled communication with the bypassed heart region and a heart fluid reservoir, where the bypassed heart region can be supplied with heart fluid via said fluid control device for heart filling and subsequent heart pumping through said fluid control device, whereby said heart may move heart fluid in said bypassed region during recovery and prior to removal of said bypassed heart region from the bypassed condition.
 5. A fluid control device as claimed in claim 2 wherein the pressure control means includes a housing with at least one inlet and at least one outlet in communication, a deformable bladder forming moveable portions in communication with said inlet and said outlet within said housing and providing the opening capable of carrying heart fluid flow passing from said inlet to said outlet, at least a portion of said deformable bladder compressible by control fluid impinging on an exterior of said deformable bladder to control heart fluid flow therethrough.
 6. A fluid control device as claimed in claim 5 wherein the control fluid impinging on said deformable bladder is or is in communication with a compressible control fluid positioned in communication externally of the moveable portions of said pressure control means providing the opening.
 7. A fluid control device as claimed in claim 5 wherein the extent of bias provided by the pressure control means is variable by varying a pressure of said control fluid.
 8. A fluid control device as claimed in claim 5 wherein the deformable bladder is engaged within said housing to pass through a cavity portion of said housing with at least one end portion thereof flared outwardly and engaged about an end portion of the housing.
 9. A fluid control device as claimed in claim 5 wherein the deformable hollow bladder is engaged with end portions thereof sandwiched between adjacent portions of end portions of said housing and connection means inserted within said housing end portions.
 10. A fluid control device as claimed in claim 2 connectable for controlled communication with said bypassed heart region between a bypassed portion of a heart aorta and a venous line of a body vascular system.
 11. A fluid control device as claimed in claim 2 wherein the bias of the pressure control means maintains a predetermined minimum pressure in said bypassed heart region, sufficient to achieve at least partial perfusion of tissue in the bypassed heart region.
 12. A fluid control device as claimed in claim 2 wherein said flow control means incorporates at least two substantially independently operable pressure control means interconnected in series.
 13. A fluid control device as claimed in claim 2 wherein the pressure control means includes a flexible portion defining a fluid passageway therein which transits a clamping means adapted for controlling a cross-sectional area of said fluid passageway, and thus flow of fluid through said pressure control means.
 14. A method of improving the removal of potential emboli from a bypassed heart region prior to removal of said region from bypass including the steps of connecting a fluid control device in communication with an output portion of said bypassed heart region, said fluid control device having a variable resistance pressure control device in communication with said bypassed heart region capable of releasing heart fluid from said fluid control device over a predetermined pressure, filling said bypassed heart region with heart fluid and allowing said heart to pump said heart fluid whilst in a bypassed condition, and whilst maintaining an inflow of heart fluid to said bypassed heart region.
 15. A fluid control device including a conduit assembly connectable for controlled communication with a bypassed heart region and a venous line of a body vascular system including a variable resistance pressure control means variably biased to a normally closed position for maintaining a predetermined level of upstream backpressure and openable under additional predetermined aortic heart fluid pressure to at least partially control fluctuating heart fluid pressure in the bypassed heart region, said fluid control device connectable with a fluid reservoir and/or oxygenation device for circulation of heart fluid between said bypassed heart region and said fluid reservoir and/or oxygenation device whilst said bypassed heart region is at least partially bypassed, said pressure control means adapted to control the fluctuating heart fluid pressure in said at least partially bypassed heart region during heart filling and subsequent heart pumping; where said heart moves heart fluid in said bypassed portions of said heart during a recovery period, prior to completion of removal of said bypassed heart region from the bypassed condition.
 16. In a system for reducing potential emboli from a bypassed heart region prior to removal of said region from bypass, a fluid control device adapted for connection in controlled communication with a bypassed heart region and a heart fluid supply for said bypassed heart region, said fluid control device including a variable resistance pressure control means adapted to control a heart fluid flow from and/or pressure in said bypassed heart region, said pressure control means normally biased towards a closed position, but openable against the bias under predetermined heart fluid pressure in said bypassed heart region to release heart fluid from said bypassed heart region, said variable resistance pressure control means providing a bias which is proportional to cross-sectional area of an opening in said variable resistance pressure control means and heart fluid pressure in said bypassed heart region.
 17. A fluid control device as hereinbefore described with reference to the accompanying drawings.
 18. A method of improving the removal of potential emboli from a bypassed heart region prior to removal of said region from bypass as hereinbefore described with reference to the accompanying drawings. 